Fix build on OS X.

pe_parse_imports() return type is void. The build on OS X uses -Wreturn-type,
which causes this error:

modules/pe.c:2293:5: error: void function 'pe_parse_imports' should not return a value [-Wreturn-type]
Merge pull request #185 from wxsBSD/pe_parse_imports_fix

Fix build on OS X.